Rayon for reinforcing rubber products



0d. 15, 1940. J A VAN LAER 2,217,826

RAYON FOR REINFORCING RUBBER PRODUCTS Filed Dec. 2, 1939 find. Willa Patented Oct. 15, 1940 PATENT I OFFICE RAYON FOB BEINFOROING B PRODUCTS Jan A. Van LaerQYonkers, N. Y., assignmto americsnlinkacorporatiomrlnkancsaeorporatfon of Delaware Application December 2, less, Serial No. 301,331

1; Claims. (a. ss-zs) The present invention relates to the preparation and construction of rayon in strand form and more particularly to the provision of an improved rayon cord especially adapted for reinforcing rubber products such as cord tires and the like. At the present time, thread of artificial origin,

and in particular, rayon, is replacing cotton to an increasing extent as a reinforcement for all types of vehicle tires. In order for such a sub-'- 0, stretching operations during the extrusion and primary treating steps, freshly spim rayon has acquired a tremendous increase in strength both in wet and dry tenacity and, which is another important factor, the elongation differential has decreased materially.

One of the major considerations and problems still confronting the industry is that of preserving the initial strength of the individual filaments comprising the thread and by the same 80 token maintaining the strength of the individual threads making up the ply or cord.

In order to handle the strand elements or constituents thereof as unitary bodies, it has been necessary to impart a twist to the various ele- 86 ments prior to, or during the formation of the cord or cable. customarily tire cords are formed in three separate twisting operations, the basic threads which are termed yarn comprise a plurality of small filaments twisted together. A pin- 40 rality of yarns are twisted together or plied to form a structure known as a ply or intermediate strand and plies thus formed are twisted with other plies to form a cord or cable. It has been determined that the proporeties of the cable are 45 dependent in part upon the degree of twist at each stage in the formation thereof. Preferably the yarn has a very low degree of twist. However, it

has been definitely determined that any twist.

imparted either to the filaments constituting the 50 thread, or to the threads or plies constituting the cord, lowers the elective strength of the cord. In other words, if the strength of a finally constructed cord is measured, it will be less than the combined strengths of the individual filal ments measured prior to twisting. As a matter of fact, if the cord is completely untwisted and the strength of the elemental filaments be remeasured, it will be found that the filaments per se have lost some of their original strength due to the several twisting operations. 5

The fact that twist influences the strength of rayon cords is evidenced by the Parker Patent No. 2,132,492. That patent is directed primarily to a twist that is low when compared to the twist disclosed by the prior art. Various ranges of twists are given for the thread, strand (intermediate) and cable (final), but the maximum at any stage does not comprehend substantially more than ten turns per inch. The patent discloses graphs plotting the strength of the cord against the turns per inch. It is obvious therefrom that an appreciable decrease in strength of the cord occurs as the turns per inch increase. The said decrease accelerates rapidly after the turns are over five per inch. Theoretically, in the range of from one to five, turns per inch the strength decreases slightly as shown in the graph (Fig. l) However, in actual practice.-it has been determined that a slight twist may not appreciably impair the strength of the final cord or cable.

As indicated above, prior to the present invention, in order to properly handle the thread and utilize the cord in reinforcing composite articles.

a substantial twist had to be employed because an untwisted strand would tend to fall apart and be come mutilated or impractical to manipulate.

It is theobiect of the present invention to provide a cord or cable composed of one or more untwisted threads held together as a unitary structure by means of an exterior support.

A further object of this invention is to'produce a number of untwisted rayon threads and bind the-same in a cord construction by means of a braided cover.

The invention additionally contemplates the manufacture of a rayon cord having a strength equal to the sum of the strengths of the individual filaments.

Another object of the invention contemplates the provision of a cord having a core consisting of untwisted filaments.

Other objects and advantages will be apparen when considered in connection with the accompanying drawings wherein 1 1g. 1 is an enlarged perspective view of one form of cord constructed in accordance with the invention;

Fig. 2 is a cross-sectional view taken on lin 2-2 of Fig. 1;

Fig. 3 shows acordhavingamcdifiedcore filaments of the core.

construction formed of three untwisted threads;

Fig. 4 is a cross-sectional view taken on line 4-4 of Fig. 3;

Fig. 5 is a second modification of the structure illustrated in Fig. 1, showing an untwisted core consisting of one large thread; and

Fig. 6 is a cross-sectional view taken on line 66 of Fig. 5.

Referring now to the drawing, the rayon cords shown therein are constructed of a multiplicity of untwisted filaments l0 bound together by means of a braided exterior or support II. The braided exterior consists of four threads indicated separately by the numerals I, 2, 3 and 4 (see Figs. 1 and 2).

A cord having the strength desired for reinforcing tires normally has a denier in the neighborhood of at least 4000, the usual 275-5-4 construction being 4125 denier. In each of the figures a core is shown consisting of 1440 filaments and having a total denier of 3300. The cord illustrated in Fig. 1 consists of twelve untwisted threads I! of 275 denier each of which is composed of 120 untwisted filaments. These threads l2 collectively make up a substantially cylindrical core. In Fig. 3, three large untwisted threads I! having 480 filaments of 1100 denier each is diclosed. Fig. 5 shows a core made up of one large thread I4, of 3300 denier.

In fabricating the cord, the individual threads may be slightly twisted, for example, one turn per inch and several of these threads may also be slightly twisted about each other prior to their disposition in a braiding machine. although neither twisting step is necessary. The threads are laid together to form a substantially cylindrical core and placed in a tubular braider. The number of threads braided around the core is optional depending upon the ultimate denier desired. In the drawing, four threads of 100 denier each are employed, which causes'the exterior to be greater than 400 denier. This is due to the fact that these braids are in helical form rather than longitudinally disposed as in the case of the The increase in denier depends, of course, on the angularity of the helices. It can be seen from the above that the total denier of the cord is slightly greater than 3700. The thread of which the braided exterior is composed, usually has a twist of from 3 to 5 turns per inch, although the twist maybe higher inasmuch as the braid per se has no effect on the final strength of the cord. For the purposes of exemplifying this invention the braid is disclosed as being made of rayon but other textile materials, such as cotton, may be employed.

In order to arrive atthe maximum allowable denier for the braided exterior, the cords, constructed in accordance with past practice, 1. e.,

twisted constructions, must be taken into consideration. The usual prior cords have been tested and found to have from 15% to less strength than the combined strengths of the individual filaments. Therefore, a cord constructed in accordance with the present invention can have a denier of from 15% to 30% less than twisted cords and still have the same strength. The denier of the braided support may accordingly range from 15% to 30% of the total denier without the latter becoming more than the denier of prior cords while still having equivalent strength. As shown in the present specific description the braided exterior is only approximately 11% of the total denier.

It can be readily seen that the present cord construction offers a number of advantages over the prior art, in that, lighter weight cords of superior strength may be used in the manufac ture of composite articles such as rubber tires, belts, etc., wherein the strength of the reinforcing elements is of the utmost importance. Moreover, the untwisted filaments are not biased against each other and therefore excessive wear and strain is avoided.

20 It is to be understood that the invention is not to be restricted to any specific construction other than one in which rayon cords are bound together by means of a braided or otherwise suitably plaited exterior, or one in which the exterior consists of a spiral strand element, such as one or more strands wound spirally in the same or opposite directions.

What is claimed is:

1. A composite cord comprising a rayon core consisting of a multiplicity of substantially untwisted filaments held together as a unitary structure by means of a sheath.

2. A composite cord comprising a rayon core consisting of a multiplicity of substantially untwisted filaments held together as a unitary structure by means of a plaited outer support.

3. A composite cord comprising a rayon core consisting of several-untwisted threads, each thread being composed of a multiplicity of untwisted filaments and held in compact cylindrical form by means of a braided cover.

4. A cord for tires and the like comprising a rayon core of at least 3300 denier and composed of several substantially untwisted threads held together by means of a braided outer support.

5. A cord as defined in claim 4 in which the braided outer support has a denier of less than 15% of the total denier of the cord.

6. A rayon cord for tires and the like comprising a core of untwisted filaments and a braided cover, the ratio of the denier of said core to the denier of the cover being at least 8:1.

7. A reinforced rubber article having embedded therein a rayon cord consisting of untwisted rayon filaments held together with a braided rayon cover.

8. A composite cord comprising a rayon core consisting of a multiplicity of substantially untwisted filaments and a braided outer support, said core having a strength equal to the combined strengths of the individual filaments.

JAN A. VAN LAER. 

